Ultraviolet radiation-induced ubiquitination and proteasomal degradation of the large subunit of RNA polymerase II. Implications for transcription-coupled DNA repair.
We have shown previously that UV radiation and other DNA-damaging agents induce the ubiquitination of a portion of the RNA polymerase II large subunit (Pol II LS). In the present study UV irradiation of repair-competent fibroblasts induced a transient reduction of the Pol II LS level; new protein synthesis restored Pol II LS to the base-line level within 16-24 h. In repair-deficient xeroderma pigmentosum cells, UV radiation-induced ubiquitination of Pol II LS was followed by a sustained reduction of Pol II LS level. In both normal and xeroderma pigmentosum cells, the ubiquitinated Pol II LS had a hyperphosphorylated COOH-terminal domain (CTD), which is characteristic of elongating Pol II. The portion of Pol II LS whose steady-state level diminished most quickly had a relatively hypophosphorylated CTD. The ubiquitinated residues did not map to the CTD. Importantly, UV-induced reduction of Pol II LS level in repair-competent or -deficient cells was inhibited by the proteasome inhibitors lactacystin or MG132. These data demonstrate that UV-induced ubiquitination of Pol II LS is followed by its degradation in the proteasome. These results suggest, contrary to a current model of transcription-coupled DNA repair, that elongating Pol II complexes which arrest at intragenic DNA lesions may be aborted rather than resuming elongation after repair takes place.
Ratner
J N
JN
Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Balasubramanian
B
B
Corden
J
J
Warren
S L
SL
Bregman
D B
DB
D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors; D004260:DNA Repair; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D012319:RNA Polymerase II / Q000378:metabolism*; D014158:Transcription, Genetic / Q000528:radiation effects*; D014452:Ubiquitins / Q000378:metabolism*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D009097:Multienzyme Complexes; D014452:Ubiquitins; D012319:RNA Polymerase II; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex